Free & Total Chlorine: What You Need to Know

It is vital to keep measurements of your pool’s chlorine levels. Chlorine is essential to sanitizing your pool keeping you and your family safe.

Chlorine can often be a source of confusion as there are three distinct kinds: free chlorine, combined chlorine and
total chlorine. For the purpose of this article, we will be
focusing on free and total chlorine, but will cover the basic
definitions of three versions.

Our friends at Swim University classify the three types of
chlorine in the following ways:

3 Types of Chlorine

  • Free Chlorine – This is the chlorine that you usually test for in your pool water. Free chlorine is able to sanitize your pool. Your pool water should have between 1 and 3 parts per
    million (ppm).
  • Combined Chlorine – Chlorine that’s been used up by the sanitation process is called combined chlorine. While it’s still in the water, its ability to sanitize is reduced compared to free chlorine.
  • Total Chlorine – Total chlorine is the sum of both free chlorine and combined chlorine.

What’s the Difference? Let’s Do the Math.

As Chemical Engineers, the science behind chlorine is our specialty! Let’s begin with this simple formula for chlorine:

FC + CC = TC

“When chlorine is added to your pool, it reacts with the
water to form hypochlorous acid and hypochlorite ion. These compounds together form what we call free chlorine.

Once this chlorine begins to react with the contaminants in the water, such as nitrogen and ammonia, it becomes combined chlorine.

In this state, the chlorine isn’t as effective at sanitizing
compared to free chlorine. Your goal is to make sure your pool is sanitized. You want to make sure your free chlorine levels stay in check.

For example, if your free chlorine levels and total chlorine levels are the same, then there’s no combined (or used chlorine) in your water. If your total chlorine level is higher than the free chlorine level, the difference of the two are the combined
chlorine levels.” – Swim University

Your combined chlorine should be zero, meaning your free chlorine and total chlorine (what gets tested) are equal.

To maintain the highest quality water in your pool, it is
important that you understand the math. By determining how much chlorine is optimal to add to your pool water, you will
ultimately reach the perfect balance and in doing so, kill the harmful contaminants in the water making your pool safer for swimming.

For example, if you test your pool water and the combined chlorine levels appear to be rising, this is a good indicator that it is time to add more chlorine to your pool to assist in sanitation. Conversely, if the combined chlorine levels appear to be low after testing, you may not need to add anything to your water at that time.

Safety Matters

We hope this gives you a better understanding of chlorine’s role in keeping your pool water safe and clean all season long, and that you have an easier time adjusting your pool’s chlorine levels for optimal sanitation. A clean and healthy pool maximizes your swimming and relaxation time and who doesn’t want that?!

Choose Hassle Free Pool Care and let our expert technicians maintain your healthy pool or stop by our Retail Store for a Free Water Test or to purchase a Chlorine Test Kit if you prefer to do it yourself.

Check out the two articles below from Aqua Magazine to learn more about the importance of chlorine in your pool water.

Chloramines in Source Water 

Is Superchlorinating The Best Way To Eliminate Chloramines?

 

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